End cap for fluorescent lamp



Nov. 20, 1956 R. B. THOMAS 2,771,589

END CAP FOR FLUORESCENT LAMP Filed Dec. 14, 1954 2 Sheets-Sheet 1INVENTOR. 2 RALPH BURGE$S THOMAS BYM all/W ATTOR NEY' Nov. 20, 1956 R.B. THOMAS END CAP FOR FLUORESCENT LAMP 2 Sheets-Sheet 2 Filed Dec. l4,-1954 FIG.4

FIG.3

INVEN RALPH BURGESS T A TTOR u E Y.

FIG. 5

United States Patent O END CAP FOR FLUORESCENT LAMP Ralph BurgessThomas, Salem, Mass., assignor to Sylvania Electric Products Inc.,Salem, Mass., at corporation of Massachusetts 4 Application December 14,1954, Serial No. 475,221 4 Claims. (31. 339-444 This invention relatesto fluorescent lamps and more particularly to highvoltage fluorescentlamps in the form of tubes having filament lead-in terminals supportedin recessed caps at both ends of the tube.

Conventional high-voltage tubular lamps of the fluorescent type employglass tubes or envelopes and hitherto have had filament lead-interminals projecting outwardly from a cap at each end. These terminalsare adapted to fit into conventional lamp-holders and are adequate fromthe point of view of electrical contact. However, a major disadvantagelies in the fact that such lamps are electrically conductive and maypresent a serious danger of shock if the person who installs one of themis not perfectly insulated from ground and happens to be touching theoutwardly projecting terminals at one end of the tube while theterminals at the other end are in con tact in the lamp holder.

It is an object of my invention to provide, in connection with caps atboth ends of high voltage fluorescent tubes, a filament lead-in terminalsupporting arrangement by means of which danger from electrical shock issubstantially eliminated.

A further object of my invention is to provide a filament lead terminalarrangement for such tubes which will be secure against random movementof the filament leads within the cap.

A still further object of my invention is the provision of alow-resistance electrical connection between the lamp and the lampholder into which it is installed.

In the accomplishment of these and other objects of my invention in apreferred embodiment thereof, I employ a high-voltage substantiallycylindrical fluorescent tube having lead-in terminals supported in capsat both ends thereof.

Both caps have recessed portions in which the filament lead-in wires areso disposed and secured that danger of accidental contact with theselead-in wires is avoided.

It is a particular feature of my invention that the lead-in wires arefirmly anchored Within the caps such that random movement thereof iscompletely eliminated.

It is still another feature of my invention that the lead-in Wires aresecured within the caps in such a man net that a clean enlarged .area ofelectrical contact is provided. The high degree of heat required invarious processes prior to mounting of the caps encourages rapid surfaceoxidation of the lead-in wires. A contact between such a surface andlamp-holder contact elements would produce a connection of undesirablyhigh electrical resistance in the low voltage filament heater circuitthereby impairing the useful life of the lamp if not actually renderingit inoperative. To secure the lead-in wires, my invention utilizes aneyelet which may be silver plated for better electrical contact and hasa head section presenting to the lamp holder an enlarged electricalcontact area. Furthermore in the process of anchoring, the eyeletabrades the lead-in wire thereby creating a low resistance connectionbetween the eyelet and the lead-in Wire.

Further objects and features of this invention will be best understoodand appreciated from. the following detailed description of a preferredembodiment thereof, selected for purposes of illustration and shown inthe accompanying drawings, in which:

Figure l is a view inside elevation showing one end in partial crosssection of an illustrative embodiment of this invention. 1

Figure 2 is an enlarged view of perspective of the boss on a cap showingone eyelet in place and one eyelet exploded for clarity.

Figure 3 is an enlarged view in cross section taken along the line 33 ofFigure 2.

Figure 4 is an enlarged View in cross section taken along the line 3-3Figure 2 showing an alternative method of anchoring the lead Wire.

Figure 5 is an enlarged view in cross section taken along the line 5-5Figure 2.

Figure 6 is an enlarged view in cross section taken along the line 6-6Figure Z.

Figure 1 presents a general view of a tubular fluorescent lampincorporating the invention. On each end of a glass envelope 11 ismounted an end cap 12 bonded to the glass by means of a quantity ofcement 10. The cap 12 in this preferred embodiment consists of a base13, an upstanding boss 14 molded integral with the base 13 ofphenolformaldehyde or similar material and a depending metal skirt 15molded into the base 13. Lead-in wires 16 project from a glass stempress 17 of the envelope 11 upwardly or outwardly, as shown in Figure 2,through an open passage 18 in the boss 14, then turn in opposite lateraldirections to enter slot 19 Where they terminate in pockets 20.

An eyelet 21, or cylindrical plug, having a body portion 22 and a head23 is inserted into thepocket 20 in contact With the lead-in wire 16.The eyelet 21 is of such size that it is deformed in the area 24, asshown in Figs. 5 and 6, by the lead-in wire 16 which is thereby heldunder compression or frictional engagement. The head 23 of eyelet 21 isof a diameter greater than the width of the slot 19 so that in theprocess of insertion the head 23 is bent upwardly to form a ratchet-likeengagement, which will dig into the side walls 25 as shown in Figure 5to resist outward axial movement.

The lead-in wires 16 may be inserted into pockets 20 in several ways.One such method is to form a loop in the end of lead wire 16 which isdisposed downwardly or inwardly adjacent to inner walls of pocket 20,then upwardly or outwardly adjacent to an outer wall of the said pocketthereby contacting the periphery of eyelet 21 in two places as shown inFigure 3. On the other hand, a method which is preferred because itfacilitates insertion of eyelet 21 is to provide a shorter length tolead wire 16 which is disposed adjacent only to the inner Walls ofpocket 20 at least part of the way down as shown in Figure 4.

Numerous minor variations of the preferred embodiment of my inventionwill now be apparent to those skilled in the art. For example the lampof the preferred embodiment need not be straight but may as well beformed in various contours. Again the upstanding boss 14 need not bemolded integral with the base 13, and on the other hand skirt 15 neednot be metallic but may be of phenol-formaldehyde or similar materialintegrally molded to base 13 so long as the female terminal elements ofmy invention are employed. Other modifications will be apparent andtherefore it is not intended to confine the invention to the preciseform herein shown but rather to limit it in terms of the appendedclaims.

What I claim is:

1, In combination with a high voltage tubular fluorescent lamp having aglass envelope and filament lead-- in Wires projecting from one endthereof, a cap mounted on the end of said glass envelope around saidlead-in wires comprising a base, an upstanding elongated boss integralwith aid base, said boss having an upper end wall, internal wallsdefining an open passage from the outside through said boss and saidbase to said envelope, the upper end Wall of said boss being indented toform a longitudinal slot therein, a pocket in said slot on each side ofsaid passage, said lead-in-wires extending upwardly through said passageand laterally adjacent to thebottom wall of said slot, one of saidlead-in wires terminating in each of said pockets, and an eyelet infrictional engagement with each of said lead-in wires and the walls ofone of said pockets.

2. The cap defined in claim 1 further characterized by the eyelet havinga head section in ratchet-like engagement with the side walls of saidslot whereby said eyelet is retained in said pocket against axialmovement.

3. A cap assembly adapted to being mounted on an end of a tubularfluorescent'lainp having a glass en- 20 velope and filament lead-inwires projecting therefrom comprising a base, an upstanding elongatedboss integral with said base, said boss having an upper end wall, in-

ternal walls defining an open passage from the outside through said bossand said base to said envelope, the upper end wall of said boss beingindented to form a longitudinal slot therein, a pocket in the bottomwall of said slot on each side of said passage, said passage providingan upward path and said slot a recessed lateral path to a point oftermination in said pockets for said lead-in wires, and an eyelet infrictional engagement with each of said lead-in Wires and the walls ofone of said pockets.

4. The cap assembly defined in claim 3 further characterized by theeyelet having a head section in ratchetlike engagement with the sidewalls of 'said slot whereby said eyelet is retained in saidpocketagainst axial movement.

References Cited in the file of this patent UNITED STATES PATENTS2,392,661 Greiner Jan. 8, 1946 2,451,900 Zambakian Oct. 19, 19482,465,797 Gooskens Mar. 29, 1949

